The paper describes ways to examine how digital libraries are valued by their users, and explores ways of permitting the allocation of resources to areas of user-identified need. Pertinent models from marketing, economics, and library assessment and evaluation are reviewed, focussing on the application of the LibQUAL+TM and CAPM methodologies. Each methodology, which was developed independently, provides a useful framework for evaluating digital library services. The paper discusses the benefits of a combined methodology that would provide even greater potential for evaluation of digital library services.